1. Field of the Invention
The present invention relates to a novel oiliness agent comprising a carboxylate of a layered crystalline composite metal hydroxide. More specifically, the invention relates to an oiliness agent useful as an emulsifier, as a thixotropy-imparting agent, as a viscosity-imparting agent and as a base material for cosmetics.
2. Description of the Prior Art
Emulsions can roughly be divided into two types; i.e., those of the oil-in-water (O/W) type and those of the water-in-oil (W/O) type. The former emulsions can be represented by a mayonnaise in which oil particles are dispersed in water, and the latter emulsions can be represented by a margarine or a butter in which water particles are dispersed in oil.
Among these emulsions, the O/W type emulsion in which a small amount of oil is dispersed in a large amount of water can be prepared relatively easily, but it is not necessarily easy to prepare the W/O type emulsion in which a large amount of water is dispersed in a small amount of oil.
As a known example of the water-in-oil type emulsion, Japanese Unexamined Patent Publication (Kokai) No. 81827/1982 discloses the one comprising a branched chain nonpolar oil, a nonionic liquid emulsifier, a reaction product of a sodium-magnesium-fluorotrisilicate-trioctahedral-montmorillonite-clay and a quaternary ammonium salt, a water-soluble magnesium salt and water, 75 to 98% by volume of the emulsion being of the aqueous phase, and 25 to 2% by volume of the emulsion being of the oil phase.
Further, Japanese Unexamined Patent Publication (Kokai) No. 151351/1988 discloses a water-in-oil type emulsified composition comprising, as essential components, a water-swelling clay mineral, a nonionic surfactant, an oil and water.
Japanese Unexamined Patent Publication (Kokai) No. 48228/1995 discloses a rouge composition comprising an organic modified clay mineral obtained by treating a water-swelling clay mineral with a quaternary ammonium-type cationic surfactant and a composite lipid or a nonionic surfactant, and an oil and a water-phase component.
However, the water-in-oil type emulsions taught in the above prior arts use a clay mineral in which the quaternary ammonium salt is incorporated among the layers as well as the nonionic surfactant. Besides, the organic clay mineral emits its particular odor, tends to be colored upon the passage of time, and stimulates the skin to a degree which is not negligible. Therefore, it has been desired to provide an emulsifier to substitute for the above emulsions.
In preparing the known water-in-oil type emulsions as pointed out already, much limitation is imposed on the surfactant, on the method of mechanical stirring, on the order of mixing, and on selecting various conditions such as temperature and the like.
Besides, most of the water-in-oil type emulsions that are formed are not still capable of satisfying the dispersion stability and the moisture retaining property to a satisfactory degree. It has therefore been eagerly desired to provide a water-in-oil type emulsion that can be easily prepared and that exhibits excellent dispersion stability and moisture retaining property.
It is therefore an object of the present invention to provide an oiliness agent which can be effectively used as an emulsifier for forming a water-in-oil type emulsion exhibiting excellent dispersion stability and moisture retaining property without emitting odor and without having a tendency of being colored.
Another object of the present invention is to provide an oiliness agent exhibiting very excellent emulsifying property with an oil, swelling property, thixotropy-imparting property, sedimentation-suppressing ability and viscosity-imparting property.
A further object of the present invention is to provide a water-in-oil type emulsion which can be effectively used as a base material for cosmetics, maintaining excellent dispersion stability and moisture; retaining property.
According to the present invention, there is provided an oiliness agent comprising a carboxylate of a composite metal hydroxide having a chemical composition represented by the following general formula (1),
M2aM3x(OH)y(A)z.nH2Oxe2x80x83xe2x80x83(1) 
wherein,
M2 indicates a divalent metal,
M3 indicates a trivalent metal,
A indicates an anion of an aliphatic carboxylic acid,
a, x, y and z are numbers satisfying the following formulas:
a greater than 0, 
3x+2axe2x88x92yxe2x88x92mz=0 (wherein m is a valency of anion A), 
0.3xe2x89xa6a/xxe2x89xa6=2.5 
1.5xe2x89xa6y/(a+x)xe2x89xa63.0 
1.0xe2x89xa6(a+x)/zxe2x89xa620.0, and 
n is a number of not larger than 7.
In the oiliness agent of the present invention, it is desired that the carboxylate of the composite metal hydroxide contains at least zinc (Zn) as a divalent metal M2. When divalent metals other than Zn are indicated by Q, it is desired that the carboxylate of the composite metal hydroxide has a chemical composition expressed by the following general formula (1a):
(Zn)p(Q)qM3x(OH)y(A)z.nH2Oxe2x80x83xe2x80x83(1a) 
wherein,
M3, A, b, x, y and z are as defined in the above general formula (1),
Q indicates a divalent metal other than Zn, and
p and q are the numbers satisfying the following formulas,
p+q=a (a is as defined in the general formula (1)), and 
p/(p+q)xe2x89xa70.1. 
It is most desired that the divalent metal Q other than zinc, is magnesium. It is further desired that the trivalent metal in the carboxylate of the composite metal hydroxide is aluminum (Al), and anion is a monovalent fatty acid having carbon atoms in a number of from 10 to 22 and, particularly, from 12 to 22.
The oiliness agent of the present invention can be effectively used as an emulsifier or a dispersant, as a thixotropy-imparting agent and as a viscosity-imparting agent. The water-in-oil emulsion (W/O emulsion) prepared by using the oiliness agent as an emulsifier, exhibits excellent dispersion stability and moisture retaining property without emitting odor or without the tendency of being colored, and is very useful as a base material for cosmetics.